Colored hydrogel objects and their production-containing a water-insoluble opaquing agent

ABSTRACT

Shaped organic polymer hydrogels, especially contact lenses, are provided with opaque or translucent coloring so as to be capable of masking effectively any underlying color, e.g. the natural color of the eye. The hydrogel may be rendered opaque by precipitation in situ of a white or yellow water-insoluble, inorganic or organic material e.g. barium sulphate or an optical brightener and then colored with a suitable dyestuff.

This is a continuation of application Ser. No. 07/134,048, filed12-17-87.

The invention relates to colouring hydrogel objects to introduce coloursdesired for either protective masking or cosmetic purposes, and moreparticularly to colouring medical devices, such as ophthalmic contactlenses, for cosmetic or prosthetic reasons, or to protect the eyes fromexcessive light.

Several methods have been previously used to colour water-absorbentplastic articles using solvent, azoic and vat dyes, see, for example thefollowing patents:

    ______________________________________                                        MESHEL          British Patent No. 1,547,525 (1979);                          KOBERLEIN       U.S. Pat. No. 2,524,811 (1950);                               BRISTOL & SHERE U.S. Pat. No. 3,519,462 (1970);                               WICHTERLE       U.S. Pat. No. 3,679,504 (1972);                               TANKA           U.S. Pat. No. 4,157,892 (1979).                               ______________________________________                                    

One of the main drawbacks of the processes of the above-mentionedpatents, is that the colours produced are transparent. Consequently ifan article such as a hydrogel contact lens is coloured in one of theseways, the effects obtainable are strictly limited. More particularly, ifit is desired to change the colour of an eye, the colour obtained is theresultant of a combination of the natural colour of the eye and thecolour of the contact lens. For example, a contact lens tinted with atransparent green colour will produce significantly different coloureffects when placed on blue, green or grey eyes. Furthermore, it is notpossible with such transparent coloured articles to produce any dramaticcolour changes on people with dark eyes, such as brown or hazel eyes.Their use is consequently limited to light coloured eyes such as blue,green or grey eyes.

It has been proposed in U.S. Pat. No. 3,476,499 (Wichterle) toprecipitate an insoluble material in a hydrogel-type lens so as toabsorb light. For example an impregnating agent is applied to one faceof such a lens and a precipitating agent to the opposite face so thatthe two agents interact within the lens to form a solid water-insolubleprecipitate. However it is disclosed that it is not always easy toobtain a precipitate of the desired density. For example if bariumchloride solution is first applied to a hydrogel lens followed bysulphuric acid, most of the expected precipitate forms on the lenssurface and can readily be removed by wiping.

The present invention provides a method for colouring hydrogels and inparticular for producing opaque or translucent colourations in atransparent hydrogel article. As compared with the process of U.S. Pat.No. 3476499, the new process is more reliable and more flexible. Whilethe following description relates mainly to colouring hydrogel contactlenses, it will be understood that the method of the invention can inprinciple be used to colour any shaped article made of an organicpolymer hydrogel. Using the new method it is possible to change thecolour of any eye, whether brown, blue, hazel, green, grey or any othercolour. This is achieved by introducing into a contact lens componentswhich both provide the desired tint, and mask the colour of the naturaleye, so that only the colour of the tint is effective. These componentsmust be translucent or opaque to light in order to achieve this effectand must be capable of being formed in a hydrogel matrix and be capable,in the case of a hydrogel contact lens, of standing up to the cleaningor disinfecting regimes used in their care, and must not leach out ofthe lens matrix. They must also, of course, be physiologicallyinnocuous. Preferably these components are not applied to the wholesurface of the hydrogel, but only to selected areas, and especially anarea corresponding to the iris of the eye, using suitable application,e.g. masking or printing, techniques.

The invention accordingly provides shaped organic polymer hydrogelscontaining within the gel an opaque or translucent, physiologicallyinnocuous water-insoluble material in an amount sufficient to render atleast part of the said hydrogel opaque or translucent, and a colouringagent for the hydrogel in at least part of the areas which have beenrendered opaque or translucent by the said water-insoluble material. Theopaque or translucent water-insoluble material may itself be slightlytinted, but the tint is mainly or completely provided by a separatematerial, and more particularly by a disperse, solvent, vat, azo, orreactive dyestuff.

The invention also provides a method of making such a hydrogel whichcomprises applying to a shaped organic polymer hydrogel a solution of awater-insoluble material or a precursor therefor under conditions suchthat the said solution penetrates substantially into the hydrogel, andthen an agent to precipitate the water-insoluble material in situ in thehydrogel and colouring at least part of the area in which theprecipitate forms before, during, or after the formation of the saidprecipitate. It is important to ensure that the first solutionsubstantially generates the hydrogel so that the precipitate is formedwithin, and not on, the hydrogel surface. With hydrogels containinglarge amounts of water, such penetration is automatic. With otherhydrogels it may be necessary to include in the first solution aswelling agent for the hydrogel which swells the hydrogel more thanwater to ensure that adequate penetration by the solution takes place.Suitable swelling agents include alcohols such as methanol or ethanol,acetone, ethylene glycol monomethylether and dimethylformamide.

The hydrogel material to which the invention is applied may be any knownorganic polymeric hydrogel of the kind out of which contact lenses aremade, but is preferably a hydrogel as described and claimed in ourBritish Specification No. 2087408. Such hydrogels combine a high watercontent and adequate mechanical properties with a low degree ofcross-linking corresponding to less than 1% of cross-linking agent inmany cases.

An aqueous solution of a water-soluble salt may be first applied to thehydrogel followed by a solution of a second reagent which reacts withthe salt to produce a water-insoluble, opaque or translucent,physiologically innocuous precipitate. Suitable water-soluble salts arebarium salts such as the chloride or nitrate, in which case the secondreagent may be sulphuric acid or a water-soluble sulphate which reactswith the barium salt to produce white, highly water-insoluble bariumsulphate.

In an alternative method a solution of a water-insoluble material in anorganic solvent capable of penetrating the hydrogel may be applied tothe hydrogel and the water-insoluble material then precipitated in situby application of water to the hydrogel. This method is preferred whenthe water insoluble material is organic.

Whichever method is used, the temperature at which the opaqueprecipitate is formed in the hydrogel is not critical and may be forexample a temperature from ambient temperature up to 5° C. lower thanthe boiling point of the reaction medium.

The treatment may be repeated if necessary to increase the opacity ofthe precipitate formed. Generally speaking the amount of water-insolublematerial should be sufficient to mask the natural colour of the eye.

The invention is especially useful for making coloured contact lenses inwhich an area corresponding to the iris of the eye is coloured and areascorresponding to the pupil and the periphery of the lens are lefttransparent. Because the iris area is opaque, the new contact lenses areable to mask the natural colour of the eye and thus provide thepossibility of lightening the eyes cosmetically. Similarly the newcontact lenses may be used to mask eyes which are unnatural inappearance e.g. as a result of injury. In the latter case, the partoverlaying the pupil should be dark coloured and preferably opaque.

The opaque or translucent material can be applied to the hydrogelbefore, after, or together with the colouring material, and the lattermay be applied to the same areas as, or at least partly to areasdifferent from, those covered by the opaque or translucent material.

A wide variety of inorganic or organic materials can be used as theopaque or translucent component. In principle any material which isopaque to light, or substantially opaque, which is physiologicallyinnocuous and which is not leached from the lens by the eye secretions,can be used. The preferred inorganic compounds are water- insolublemetal compounds such as hydroxides, chlorides, oxides, sulphates, orsulphides of metals, such as aluminium, calcium, barium, silver, ortitanium. The colour of the material must be compatible with the coloureffect desired, and for this reason the preferred components are thosewhich are white to yellow in colour. A preferred compound is bariumsulphate, which can be precipitated as a white, non-toxic,water-insoluble solid in a hydrogel matrix by first soaking the matrixin an aqueous or aqueous/alcoholic (e.g. aqueous methanolic) bariumchloride solution and then precipitating BaSO₄ by soaking the matrix indilute sulphuric acid.

The preferred organic compounds are fluorescent or optical brightenerswhich are insoluble in water, but preferably solvent soluble, and whiteto yellow in colour. Various types of fluorescent brighteners are listedin KIRK OTHMER, ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY, VOL 4 Pages213-226. Translucent to opaque precipitates in hydrogels can be obtainedfrom fluorescent brighteners including, for example, those marketedunder the trade names, Leucopure, Hostalux, Multraphor, Uvitex andFluolite, which are relatively insoluble in water but soluble in organicsolvents.

Suitable dyes which can be used to tint the hydrogels are ProcionTurquoise SP-26, Procion Blue P-GR, Procion Brown P-GR, Procion OrangeP-2R, CI Solubilized Vat Orange 5, CI Solubilized Vat Blue 6, CISolubilized Vat Green 1, CI Solubilized Vat Brown 1, CI Dispersol Violet28, Savinyl Blue GLS, Savinyl Green 2GLS, and Waxoline Red GPFW. For anatural effect the colouring agent should be applied in such a way thatthe intensity of colour is essentially constant over the whole of thecoloured area apart from any deliberate patterning that may beintroduced.

If desired patterns may be incorporated into the opaque material and/orthe colouring agent, in order better to simulate the natural appearanceof the eye. For example, by using standard printing (especially screen,pad or ink-jet printing) techniques, the opaque material may be formedin a pattern in the hydrogel. Such a pattern may be of continuous,straight, curved or zig-zag lines or of solid shapes such as triangles,parabolas, ellipses, or rectangles. The colouring may take place beforeor after such a printing operation. Similarly the colouring agent may bedeposited as a pattern in a similar way and using similar techniques.Moreover, more than one colouring agent can be used.

For example a contact lens coloured in accordance with the invention maybe further coloured by applying a different transparent dyestuff todeposit a pattern over the iris section. To resemble the natural irispattern, this second dyestuff is preferabIy a dark shade, e.g. black,grey, navy blue or brown. It may be applied by standard printingtechniques. This pattern may be solid, continuous or intermittent, andshould preferably cover at least 5 percent of the tinted erea. By usingthis technique, the colour of the contact lens in use will be theresultant of the transparent tint enhanced with the pattern of thesecond transparent colour. Moreover if the opaque backing is patterned,it adds to the combined effect.

The invention is illustrated by the following Examples:

EXAMPLE 1

A saturated aqueous solution of barium chloride was applied to ahydrogel contact lens, based on a copolymer of N-vinyl-pyrrolidone and ahydrophobic methacrylate, as described in British Pat. No. 2087408,having a water content of 77%, for 10 minutes. The central 4 mmpupillary area and 2 mm of the outer peripheral area of the lens weremasked. The lens was then treated with 2% H₂ SO₄ solution for 2 minutes.An opaque pattern consisting of a white precipitate of barium sulphatewas formed in the lens, the pupillary and peripheral areas of the lensbeing left clear.

The lens obtained was coloured with a solution of a reactive dye(Procion Green P-4BL) in water for 2 minutes, the pupillary andperipheral areas being masked. A green opaque lens was obtained whichhad clear pupillary and peripheral areas. This lens was placed on abrown eye and was effective in masking the brown colour and turning theeye to green.

Similar results are obtained if the lens is tinted with other reactive,solubilized vat colours, solvent or disperse dyestuffs dissolved inwater or a solvent such as acetone. The different coloured lensesobtained were effective in changing the colour of brown eyes.

EXAMPLE 2

Example 1 was repeated using a saturated barium chloride solution inaqueous 30% or 50% methanol instead of water. A more dense opaqueprecipitate was obtained, than in Example 1 indicating a deeperpenetration of the barium sulphate into the lens matrix, caused by theadditional swelling of the hydrogel by the methanol. The opaque lensobtained (after tinting as described in Example 1) was placed on a browneye and was effective in masking the brown colour.

The same result is obtained if the lens is first tinted and then treatedas described in Example 2.

Example 3

An opaque white precipitate was obtained in a 2-hydroxy-ethylmethacrylate hydrogel, having a water content of 38%, using the methoddescribed in Example 2. This hydrogel was tinted as described in Example1 to produce a coloured lens in accordance with the invention.

EXAMPLE 4

Example 2 was repeated using aqueous Aluminium Sulphate or Zinc Chloridesolution, followed by Sodium hydroxide solution, to form an opaqueprecipitate of insoluble Aluminium or Zinc hydroxide in the hydrogel. Amixture of barium sulphate and aluminium hydroxide was also precipitatedin the lens using a two stage process.

EXAMPLE 5

An N-vinyl-2-pyrrolidone copolymer hydrogel was steeped in a solution ofan optical brightener sold under the trade name Hostalux NSM (0.25g.) inethylene glycol monomethyl ether (20g.) for 5 minutes. The hydrogel wasremoved and rinsed in ethylene glycol monomethyl ether for 5 seconds,and then steeped in distilled water. A translucent to opaque yellowdeposit was formed in the hydrogel which did not leach out in water.When this hydrogel was tinted with a blue reactive dye, the hydrogelassumed a greenish blue colour, which was successful in masking thecolour of a brown eye.

Essentially the same result is obtained if the ethylene glycolmonomethyl ether is replaced by dimethylformamide, tetrahydrofuran,acetone, methanol/acetone (50/50), methanol/ethylene glycol monomethylether (50/50), or tetrahydrofuran/dimethylformamide (90/10), as solventfor the optical brightener.

The vinyl-pyrrolidone based hydrogel can be replaced by a hydrogel basedon 2-hydroxy ethyl methacrylate and the same result obtained.

The reactive dye may be replaced by a vat, solvent or disperse dye totint the hydrogel.

It is also possible first to apply a disperse, solvent, vat or reactivedye to the hydrogel contact lens and then to render the lens opaque bythe method in Example leaving the peripheral and pupillary areas clear.Coloured contact lenses thus obtained were effective in changing thecolour of brown eyes to the colour of the lens.

EXAMPLE 6

Example 5 was repeated using the optical brightener sold under the tradename Uvitex OB dissolved in tetrahydrofuran, ethylene glycol monomethylether, or dimethylformamide. The solution was applied to a hydrogelcontact lens to produce a translucent to opaque off-white pattern, thepupillary and peripheral areas of the lens being masked. Examples ofthese lenses were tinted with Vat, reactive, solvent or disperse dyes toproduce tinted lenses which were capable of masking a brown eye.

EXAMPLE 7

A coloured opaque lens was obtained by dissolving both the opticalbrightener sold under the trade name Hostalux NSM and a solvent bluedyestuff in acetone and applying the mixture to a hydrogel contact lenshaving a water content of 67% to produce, after precipitation of theoptical brightener and the dyestuff, a coloured contact lens capable ofchanging the colour of a brown eye.

EXAMPLE 8

An opaque white pattern consisting of a mixture of barium sulphate andthe optical brightener Uvitex OB was produced in a hydrogel contact lensusing a two stage precipitation process as described in Examples 2 and6. The lens obtained was then tinted with a reactive, vat, solvent, ordisperse dye to produce an opaque, coloured hydrogel lens capable ofchanging the colour of brown eyes.

All the lenses described in the above Examples were capable ofeffectively masking the colour of blue, green, grey or hazel eyes aswell as brown eyes.

All the dyestuffs disclosed in the above Examples were applied to thehydrogel by standard techniques employed in the dyeing or printingindustry, viz. dissolving the colourant in water and/or a solvent whichis capable of swelling the hydrogel, applying the dye solution toselected areas of the hydrogel for a fixed time, followed by evaporatingthe solvent, or fixing or oxidizing the colourant to render it, in thehydrogel matrix, insoluble in water.

EXAMPLE 9

The iris section of an opaque coloured contact lens produced inaccordance with any of the Examples 1 to 8 was overprinted with apattern of radiating straight lines by a screen printing process. Thiswas achieved by dissolving 5% solubilized vat Brown dyestuff in hotwater with 2% corn starch, and allowing the mixture to cool at roomtemperature to a paste which could be screen printed onto the hydrogellens using a doctor blade. The screen was removed, and the lens allowedto stand for 10 minutes and then oxidized in a solution of 2% sulphuricacid containing sodium nitrite to regenerate the parent vat dye. Anopaque coloured lens with patterned brown lines was obtained.

This Example was repeated using other viscosity enhancing agents, e.g.cellulose derivatives, alginates, gums, glycerol, other starches insteadof corn starch, in a quantity to prevent the colour spreading orsmudging after removing the screen, to produce patterns on the lens.

Pad printing or ink jet printing may be used in place of screenprinting.

EXAMPLE 10

Example 9 was repeated using other classes of dyestuffs such asreactive, solvent, or disperse dyestuffs using the appropriate solventto dissolve the dyestuff and a compatible viscosity enhancing agent toobtain similar patterns on the lenses.

EXAMPLE 11

Example 9 was repeated using other patterns such as curved or zig-zag orintermittent broken lines or solid shapes such as triangles, parabolas,ellipses, circles or rectangles or combinations of the above to obtain avariety of patterned lenses.

EXAMPLE 12

The opaque coloured patterns can also be formed by screen printing, padprinting, or ink jet printing techniques using suitable viscosityenhancing agents as described in Example 9, e.g. as follows.

A paste containing 2% corn starch and 10% barium chloride was made up inhot water and allowed to cool to room temperature. This paste wasprinted as a pattern consisting of straight parallel radiant lines, onthe iris section of a contact lens containing 67% water by a screenprinting process. The lens was allowed to stand for 2 minutes and thendeveloped in a 2% sulphuric acid solution to precipitate insolublebarium sulphate in the lens matrix in the form of the applied pattern.These lenses were then tinted with a solvent, reactive, disperse or vatdye as described in the foregoing Examples to give a patterned lenswhich, when placed on a dark brown eye, was effective in changing thecolour of the eye and looked natural.

Pad printing or ink jet printing may be used in place of screenprinting.

Other patterns as described in Example 11 can also be obtained. Thepatterns produced can be made of continuous lines or shapes rather thandotted lines or shapes.

I claim:
 1. A shaped organic polymer hydrogel containing within the gelan opaque or translucent, physiologically innocuous, water-insolubleprecipitate selected from the group consisting of water-insolublehydroxides, oxides, sulphates and sulphides of barium, aluminum and zincin an amount sufficient to render said hydrogel opaque or translucent,and a dye for the hydrogel selected from the group consisting ofreactive, solvent, disperse and vat dyes in at least part of those areascontaining the said water-insoluble precipitate.
 2. A shaped hydrogelaccording to claim 1 in the form of a contact lens in which the partoverlying the iris of the eye is coloured and opaque and the partoverlaying the pupil of the eye is transparent.
 3. A shaped hydrogelaccording to claim 2 in which, in the said part overlaying the iris ofthe eye, the water-insoluble precipitate is opaque, white or palecoloured, and patterned and the dye is uniform or in a pattern.
 4. Ashaped hydrogel according to claim 1 for cosmetic or prosthetic purposesin the form of a contact lens in which the part overlying the iris ofthe eye is coloured and opaque and the part overlying the pupil of theeye is dark coloured.
 5. Method of making a shaped organic polymerhydrogel containing within the gel an opaque or translucent,physiologically innocuous, water-insoluble precipitate selected from thegroup consisting of water-insoluble hydroxides, oxides, sulphate andsulphides of barium, aluminum and zinc in an amount sufficient to rendersaid hydrogel opaque or translucent, and a dye for the hydrogel selectedfrom the group consisting of reactive, solvent, disperse and vat dyes inat least part of those areas containing the said water-insolubleprecipitate which comprises applying to a shaped organic polymerhydrogel a solution of a precursor of the water-insoluble precipitateunder conditions such that the said solution penetrates substantiallyinto the hydrogel, and then an agent which interacts with said precursorto form said water-insoluble precipitate in situ in the hydrogel, anddyeing with a reactive, solvent, disperse or vat dye at least part ofthe area in which the precipitate is formed before, during or after theformation of the said precipitate.
 6. Method according to claim 5 inwhich a solution of a water-soluble salt of barium, aluminum or zinc isfirst applied to the hydrogel and a water-insoluble hydroxide, oxide,sulphate or sulphide is then precipitated in the hydrogel by applyingthereto a reagent which reacts with the said salt to produce awater-insoluble precipitate.
 7. Method according to claim 6, in whichthe said solution of a water-soluble salt of barium, aluminum or zincincludes as swelling agent for the said hydrogel, methanol, ethanol,acetone, ethylene glycol monomethyl ether, or dimethylformamide. 8.Method according to claim 5 in which the solution of the said precursoris applied uniformly or in a pattern to the hydrogel by screen printing,pad printing, or ink jet printing.
 9. Method according to claim 6 inwhich the water-insoluble precipitate is barium sulphate, aluminumhydroxide, or zinc hydroxide or a mixture thereof.
 10. Method accordingto claim 5 in which the dyestuff is applied uniformly or in a pattern byscreen printing, pad printing or ink jet printing.